This paper presents a methodology for identifying soil parameters that takes into account different constitutive equations. The procedure, applied here to identify the modified Cam-Clay parameters from a pressuremeter curve, is based on an inverse analysis approach, which consists of minimizing the function representing the difference between the experimental data and the data obtained by integrating the model along the loading path in in-situ testing. The numerical process implemented here is based on the interaction of two numerical tools; an optimization code (SiDoLo) and a general finite element code (CESAR-LCPC).